Genetic engineering methods have been used successfully to modify the fatty acid profile of elite Australian germplasm of Brassica napus and B. juncea. Co-suppression plasmids carrying oleate desaturase genes from each species have been constructed and transferred into Australian elite breeding lines of B. napus and B. juncea using Agrobacterium tumifaciens plant-transformation techniques. Modifications to existing Brassica transformation protocols and the use of an intron-interrupted hygromycin-resistance gene as the selectable marker have resulted in improved transformation efficiencies. Silencing of the endogenous oleate desaturase genes has resulted in substantial increases in oleic acid levels, up to 89% in B. napus and 73% in B. juncea.